A second sudden retreat, and the knight is shifted to its optimal position.
18... g7e5 Black follows the most forcing path. 19. d2e4  19... b7b6 But here the Chinese GM misses an important detail. 20. d1e1 A star move $1 The main threat is Ne4xc5 $1 with the total collapse of the opponent's queenside. 20... e6c6 